Camera identifiers may be declared to make scene files more readable and to parameterize scenes so that changing a
single declaration changes many values. You may declare several camera identifiers if you wish. This makes it easy to
quickly change cameras. An identifier is declared as follows.

Note: only camera transformations can be added to an already declared camera. Camera
behaviour changing keywords are not allowed, as they are needed in an earlier stage for resolving the keyword order
dependencies.